Responses of Amniotic Fluid Volume and Its Four Major Flows to Lung Liquid Diversion and Amniotic Infusion in the Ovine Fetus

Abstract

We designed experiments to allow direct measurement of amniotic fluid volume and continuous measurement of lung liquid production, swallowing, and urine production in fetal sheep. From these values, the rate of intramembranous absorption was calculated. Using this experimental design, the contribution of lung liquid to the control of amniotic fluid volume was examined. Fetuses were assigned to 1 of 4 protocols, each protocol lasting 3 days: control, isovolemic replacement of lung liquid, supplementation of amniotic fluid inflow by 4 L/day, and supplementation of amniotic inflow during isovolemic replacement of lung liquid. We found no effect of lung liquid replacement on any of the known flows into and out of the amniotic fluid. Although intramembranous absorption increased greatly during supplementation, the amniochorionic function curves were not altered by isovolemic lung liquid replacement. We conclude that lung liquid does not appear to contain a significant regulatory substance for amniotic fluid volume control.

Keywords

Fetal lung liquid swallowing intramembranous absorption.

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References

Chamberlain PF , Manning FA , Morrison I. , Harman CR , Lange IR Ultrasound evaluation of amniotic fluid volume. I. The relationship of marginal and decreased amniotic fluid volumes to perinatal outcome. Am J Obstet Gynecol. 1984;150:245-249.

Chamberlain PF , Manning FA , Morrison I. , Harman CR , Lange IR Ultrasound evaluation of amniotic fluid volume. II. The relationship of increased amniotic fluid volumes to perinatal outcome . Am J Obstet Gynecol. 1984;150:250-254.

Fischer RL , McDonnell M. , Bianculli KW , Perry RL , Hediger ML , Scholl TO Amniotic fluid volume estimation in the postdate pregnancy: a comparison of techniques. Obstet Gynecol. 1993;81:698-704.

Brace RA , Wolf EJ Normal amniotic fluid volume changes throughout pregnancy. Am J Obstet Gynecol. 1989;161:382-388.

Moore TR , Cayle JE The amniotic fluid index in normal human pregnancy. Am J Obstet Gynecol. 1990;162:1168-1173.

Anderson D. , Yang Q. , Hohimer A. , Faber J. , Giraud G. , Davis L. Intramembranous absorption rate is unaffected by changes in amniotic fluid composition. Am J Physiol Renal Physiol. 2005 ;288:F964-F968.

Brace RA Physiology of amniotic fluid regulation. Clin Obstet Gynecol . 1997;40:280-289.

Faber J. , Anderson D. , Hohimer R. , Yang Q. , Giraud G. , Davis L. Function curve of the membranes that regulate amniotic fluid volume in sheep . Am J Physiol Heart Circ Physiol. 2005;289:H146-H150.

Gilbert WM , Brace RA The missing link in amniotic fluid volume regulation: intramembranous absorption . Obstet Gynecol. 1989;74:748-754.

10.

Ross MG , Brace RA NIH Workshop Participants. National Institute of Child Health and Human Development Conference Summary: amniotic fluid biology-basic and clinical aspects. J Matern Fetal Med. 2001;10:2-19.

11.

Beall MH , van den Wijngaard JP , van Gemert MJ , Ross MG Regulation of amniotic fluid volume. Placenta. 2007;28: 824-832.

12.

Faber JJ , Anderson DF Absorption of amniotic fluid by amniochorion in sheep. Am J Physiol Heart Circ Physiol. 2002;282:H850-H854.

13.

Yang Q. , Davis L. , Hohimer A. , Faber J. , Anderson D. Regulatory response to washout of amniotic fluid in sheep. Am J Physiol Heart Circ Physiol. 2005;288:H1339-H1343.

14.

Matsumoto LC , Cheung CY , Brace RA Effect of esophageal ligation on amniotic fluid volume and urinary flow rate in fetal sheep. Am J Obstet Gynecol. 2002;182:699-705.

15.

Fujino Y. , Agnew CL , Schreyer P. , Ervin MG , Sherman DJ , Ross MG Amniotic fluid volume response to esophageal occlusion in fetal sheep. Am J Obstet Gynecol. 1997;165: 1620-1626.

16.

Daneshmand SS , Cheung CY , Brace RA Regulation of amniotic fluid volume by intramembranous absorption in sheep: role of passive permeability and vascular endothelial growth factor. Am J Obstet Gynecol. 2003;188:786-793.

17.

Brace RA , Wlodek ME , Cock ML , Harding R. Swallowing of lung liquid and amniotic fluid by the ovine fetus under normoxic and hypoxic conditions. Am J Obstet Gynecol. 1994;171: 764-770.

18.

Dickson KA , Harding R. Restoration of lung liquid volume following its acute alteration in fetal sheep. J Physiol. 1987;385:531-543.

19.

Dickson KA , Harding R. Decline in lung liquid volume and secretion rate during oligohydramnios in fetal sheep. J Appl Physiol. 1989;67:2401-2407.

20.

Sherman DJ , Ross MG , Day L. , Humme J. , Ervin MG Fetal swallowing: response to graded maternal hypoxemia. J Appl Physiol. 1991;71:1856-1861.

21.

Thurlow RW , Brace RA Swallowing, urine flow, and amniotic fluid volume responses to prolonged hypoxia in the ovine fetus. Am J Obstet Gynecol. 2003 ;189:601-608.

22.

Tomoda S. , Brace RA , Longo LD Amniotic fluid volume regulation: basal volumes and responses to fluid infusion or withdrawal in sheep. Am J Physiol. 1987 ;252:R380-R387.

23.

Brace RA , Wlodek ME , McCrabb GJ , Harding R. Swallowing and urine flow responses of ovine fetuses to 24 h of hypoxia. Am J Physiol. 1994;266:R1345-R1352.